Voltage regulators for use with electronics circuits are well known. It is also known to include a voltage regulator on the die of an integrated circuit. The difficulty with typical internal voltage regulator comes when power is first applied and the system, including the internal regulator, is initializing and reaching a stable state.
In a typical arrangement, when power is first applied an unregulated voltage source is applied to the regulator circuit. The unregulated voltage source typically may vary over a very wide range, including well in excess of twenty volts in many instances, and much higher—in excess of eighty volts—in at least some instances. More importantly, such voltages may—at least briefly at startup—be applied to the primary circuit that the regulator is designed to protect.
While the components of many integrated circuits can withstand the higher voltages, some circuits have components which cannot. Thus, for example, it is well known that certain types of transistors cannot withstand applied voltages greater than ten volts; others cannot withstand applied voltages at higher levels, but would still be damaged if those levels were exceeded.
As a result, there has been a need for a startup regulator system and method which provides appropriate protection to the load circuit during the startup process while still permitting the regulator to function once the regulator has stabilized. In addition, there has been a need for a regulator which offers protection to load circuits where the initial applied voltages exceeds the typical damage threshold for those components, for example on the order of eighty volts.